Some of the controls from Telerik.Web.UI.dll are not included in Sitefinity's toolbox, but you could refer them directly from Telerik.Web.UI namespace. RadSiteMap is included since ASP.NET AJAX Q3 2009. You can check the Telerik.Web.UI.dll version that is located in your bin.
the Telerik team
Do you want to have your say when we set our development plans?
Do you want to know when a feature you care about is added or when a bug fixed?
Telerik Public Issue Tracking
system and vote to affect the priority of the items